Shell-and-tube HE: the most common type of HE.
Large size & weight
It contains a large number of tubes packed in a shell with its axes parallel to that of the shell.
Heat transfer takes place as one fluid flow inside the tube while the other fluid flows outside the tube through the shell.
Baffles are placed in the shell to force the shell-side fluid to flow across the shell to enhance heat transfer and to maintain uniform spacing between the tubes.
Shell-and-tube HE are classified according to the no. of shell & tube passes involved.